"A notice on the chalkboard indicates that class has been moved to the science lab. The lab turns out to be empty, but Jan-di waits around, not noticing when a canister of gas rolls inside, slowly filling the room with its fumes.
When Jan-di does notice the smoke, she scrambles for the door, which is locked. All the windows have been nailed shut as well, so she pounds on the windows and screams for somebody to save her."